In order to meet a market for line marking apparatus, three different types of apparatus have been developed. Two of these types of line marking apparatus are large self-propelled machines that are used for big areas and the fast marking of roads. The largest of these are based on conventional trucks that are modified to carry over a thousand liters of paint and cover large distances. These apparatus are useful for roads with wide radius bends and are able to mark such roads quickly without reloading or stopping.
The second type are a little smaller and more manoeuvrable. It generally weighs over a tonne and is suitable for areas such as large car parks and sports fields with tighter radius bends but unrestricted access.
The third type which is most closely related to the invention, are small hand pushed machines that are used mainly for detail work around intersections or indoor painting. They are often set up with a second paint gun that can be used freehand for features that are not suited to being painted as a continuous line. An example, the second paint gun would be used to paint the arrows at intersections. This type of work is usually done with a stencil.
These third types of apparatus need to be light to be easily pushed by the operators. The weight of the machines is substantial because of the weight of the engine, the pump, the paint as well as the wheels and frame. These types of apparatus typically weigh around 100 kg. This is a substantial weight which needs to be pushed by the operator and over time places a great physical strain on the operator. It is particularly difficult for smaller operators on steep terrain or surfaces which offer more resistance such as grass on sports fields.
Manufacturers to date have addressed this by adding propulsion systems to existing hand pushed machines. This is an easy way of making these machines, more versatile. However by simply adding a propulsion unit to an existing hand push design results in an apparatus which has limited manoeuvrability. This results in an apparatus being unable or unsuitable to perform the detail work that is the main function and advantage of these small machines. The detail work generally can only be done by removing the propulsion unit and pushing the apparatus around the small areas.
The object of the present invention is to produce an apparatus which is manoeuvrable enough to do the most detail of line work and directionally stable enough to paint longer straight lines.
The applicants found that if a direct ratio steering system was used to control the directional wheel, then in the modes of operation, namely straight line marking or small radius cornering, direct ratio steering created a problem in that the steering was too fast when driving in a straight line and at the same time too slow when turning sharply. Therefore it is desirable to have a steering system which was able to retain fast steering for manoeuvring in tight spaces but have stability for straight lines.
This is addressed by a variable ratio steering system which enables the directional wheel to be able to rotate as much as 200° (ie 100° either side of straight line alignment) with the rate at which the directional wheel rotates increasing the further the wheel is rotated away from the straight line alignment.
The applicants have achieved this by using a single universal joint between the primary steering mechanism and the secondary steering mechanism. By inclining the actuator wheel of the primary steering mechanism steering wheel at an angle to the steering sprocket of the secondary steering mechanism back towards the operator, the natural operation of the universal joint to alter the speed at which two shafts turn relative to each other as the universal joint rotates can be utilised to give the effect of producing a small rotation of the directional wheel when a rotation is applied to the steering wheels effectively producing a slow rotation when the directional wheel is substantially pointed straight ahead, and producing a larger rotation when the same corresponding rotation is applied when the directional wheel is rotated out of away from the straight ahead alignment. This has the effect of speeding the steering up when turning sharply either left of right without restricting steering angle.